------------------------------------------------------------------------ *From*: P J P *Subject*: [Qemu-devel] [PATCH 2/2] scsi: check dma length before reading scsi command(CVE-2016-4441) *Date*: Thu, 19 May 2016 16:09:31 +0530 ------------------------------------------------------------------------ From: Prasad J Pandit The 53C9X Fast SCSI Controller(FSC) comes with an internal 16-byte FIFO buffer. It is used to handle command and data transfer. Routine get_cmd() uses DMA to read scsi commands into this buffer. Add check to validate DMA length against buffer size to avoid any overrun. Fixes CVE-2016-4441 Reported-by: Li Qiang Signed-off-by: Prasad J Pandit --- hw/scsi/esp.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/tools/qemu-xen-traditional/hw/esp.c b/tools/qemu-xen-traditional/hw/esp.c index 01497e6..591c817 100644 --- a/tools/qemu-xen-traditional/hw/esp.c +++ b/tools/qemu-xen-traditional/hw/esp.c @@ -82,7 +82,7 @@ void esp_request_cancelled(SCSIRequest *req) } } -static uint32_t get_cmd(ESPState *s, uint8_t *buf) +static uint32_t get_cmd(ESPState *s, uint8_t *buf, uint8_t buflen) { uint32_t dmalen; int target; @@ -92,6 +92,9 @@ static uint32_t get_cmd(ESPState *s, uint8_t *buf) target = s->wregs[ESP_WBUSID] & BUSID_DID; if (s->dma) { dmalen = s->rregs[ESP_TCLO] | (s->rregs[ESP_TCMID] << 8); + if (dmalen > buflen) { + return 0; + } s->dma_memory_read(s->dma_opaque, buf, dmalen); } else { dmalen = s->ti_size; @@ -166,7 +169,7 @@ static void handle_satn(ESPState *s) uint8_t buf[32]; int len; - len = get_cmd(s, buf); + len = get_cmd(s, buf, sizeof(buf)); if (len) do_cmd(s, buf); } @@ -192,7 +195,7 @@ static void handle_satn_stop(ESPState *s) static void handle_satn_stop(ESPState *s) { - s->cmdlen = get_cmd(s, s->cmdbuf); + s->cmdlen = get_cmd(s, s->cmdbuf, sizeof(s->cmdbuf)); if (s->cmdlen) { DPRINTF("Set ATN & Stop: cmdlen %d\n", s->cmdlen); s->do_cmd = 1; -- 2.5.5